What you just posted is proof in itself, and the denial is more proof, actually.
It could be their confusion that's keeping them out. Trying to figure out things. Have you tried talking aloud to yourself, explaining things to yourself, reading explanations to yourself, basically trying to help them understand and come to terms with things and such? Reassuring yourself and them that they're ok, you're ok, this is all ok and "normal" for what's going on, they're safe, you're safe, etc.? Self-talk can sometimes do wonders in these situations. Don't worry if you don't get replies back- just still try to talk to yourself/them in case they are listening/can listen in/can hear you. Basically take the help people have given you in understanding more about what's going on and what you've learned about DID and try to pass it on to other parts of yourself. Maybe ask your therapist for help with this? Or ideas on the situation? Or can you type to yourself instead of talk to yourself? Try typing stuff like "Hey you, read this" or something, and then try to explain things and reassure them that way.
We hope this gets better for you soon. Hang in there.
~A mixture of us(?)